While a voluminous lecture hall can present obstacles to effective teaching and learning, large classrooms containing more than 100 students also present teaching opportunities. The lecture hall offers an excellent arena for demonstrating concepts that lend themselves to demonstrations and something this author refers to as "group performances." Group performances are short, 5-15 minute activities that utilize ten or more students from the class, each performing a simple role, to demonstrate a concept or process. Effective performances take little time to organize, are visually exciting, and help to make abstract concepts tangible. In this article, the author describes two group performances that he used in large Introductory Biology lecture classes. The first helps illustrate how a nerve impulse is conducted along a nerve axon and can be carried out with the students remaining at their seats. The second demonstrates the evolutionary development of structural organization in multi-cellular organisms. This performance is more complex, but is broken down into distinct stages that make it easy to organize, coordinate, and perform. (Contains 1 figure.)